1. Field of the Invention
The present invention relates to a motor drive controller and a method for controlling a motor.
2. Description of the Related Art
In the related art, there is a drive controller for a sensorless brushless DC motor that performs advance-angle control. An example of such device is disclosed in JP-A-2005-312217.
The motor drive controller described in JP-A-2005-312217 is configured to raise and output a phase reference voltage and to generate a phase signal so as to cause an advance angle to lag, when a value of a load current detected by a load current detecting unit decreases (when a load decreases). The motor drive controller lowers and outputs an advance-angle reference voltage and generates the phase signal to cause the advance angle to advance, when the value of the detected load current increases (when the load increases). Accordingly, the motor drive controller performs optimal advance-angle control depending on the load.
In this related art motor drive controller, since a torque is required and thus the value of the load current increases at the time of rotation start of a motor, the advance reference potential is controlled to drop and decrease.
However, the motor drive controller described in JP-A-2005-312217 performs optimal advance-angle control depending on the load at the time of rotation start of the motor, but may have a problem in that it is not possible to avoid loss of synchronism.
Accordingly, there has been a demand for a motor drive controller that can perform more optimal advance-angle control.